In internal combustion engines, particularly reciprocating internal combustion engines, “blow-by” gas stream is created due to the imperfect seal between the piston and the cylinder wall. These blow-by gases are thus able to get into the crankcase and must therefore be vented from the crankcase again. At the same time, it is critically important that the pressure in the crankcase remains within certain limits. If the pressure in the crankcase is too high, oil from the crankcase may escape from the engine block through gaskets. If the pressure is too low, oil may be sucked out of the crankcase by the crankcase venting device. Both cases are undesirable, so the pressure in the crankcase must be kept within certain limits.
The blow-by gases vented from the crankcase typically contain an oil mist, which must be separated in an oil mist separating device if the loss of oil due to the crankcase venting device is to be minimised. A certain differential pressure is needed for the oil mist separating device, and when the internal combustion engine is not under load this is supplied by the pressure difference between the crankcase and an intake tract of the internal combustion engine behind a throttle in which a negative pressure prevails. When the internal combustion engine is under load, there is not enough of this negative pressure available. For this reason, crankcase venting devices with additional pumping devices are known.
Such a crankcase venting device with an additional pumping device is known from DE 10 2006 024 816 A1 for example. However, the output of the pumping device must be controlled so that the pressure in the crankcase does not exceed the permitted limits. This is why a pressure measuring device is typically provided in the crankcase.